Photo-electronic device and method of producing the same

ABSTRACT

A photo-electronic device including a package having a main body portion containing parts including a photoelectric conversion element at inside thereof and a guide portion a front end of which faces the photoelectric conversion element for guiding, in a penetrated state, an optical fiber for transmitting and receiving light to and from the photoelectric conversion element, in which the optical fiber is fixed to the guide portion by adhering agent at the guide portion and portions of the main body portion including the photoelectric conversion element and a front end portion of the optical fiber are covered by a protective film formed by a resin transparent to the light and a dam is provided between the protective film and the adhering agent such that the protective film and the adhering agent are not brought into contact with each other.

This is a divisional application of U.S. Ser. No. 09/800,502, filed Mar.8, 2001 now allowed.

BACKGROUND OF THE INVENTION

The present invention relates to a photo-electronic device(semiconductor optical module) and a method of producing thereof,particularly to a technology effectively applied to a technology ofproducing a photo-electronic device capable of preventing breakage of anoptical fiber core line comprising a core and a clad and extended in apackage and capable of preventing a deterioration in transmissionefficiency of light.

There is used a photo-electronic device integrated with a semiconductorlaser (semiconductor laser element: semiconductor laser chip) as a lightsource for an information processing apparatus or a light source foroptical communication. As an example of a photo-electronic device, thereis disclosed, in Japanese Patent Laid-Open No. 282369/1998 or JapanesePatent Laid-Open No. 307235/1998, an optical communication apparatus(semiconductor laser module) forming a package by a case and a lid (cap)comprising plastics (resin) formed by a transfer mold process,containing a semiconductor laser (laser diode) or a photo detector(photo diode) and extending an optical fiber to inside and outside ofthe package.

Further, portions of a pad (pad portion) and a lead frame for fixing asilicon substrate, are embedded in the case simultaneously with thetransfer mold operation. The silicon substrate is fixed with thesemiconductor laser. The optical fiber extended to inside and outside ofthe package is constructed by a structure in which the optical fibercore line is covered with a cover member up to a middle of the packageand a front end thereof is a bare optical fiber at which the opticalfiber core line is exposed by removing the cover member. The opticalfiber core line is constituted by the core and the clad covering thecore and both of them comprise, for example, quartz and are brittle andeasy to break by external force.

Further, in the package, the semiconductor laser is covered withtransparent gel-like resin comprising silicone resin.

SUMMARY OF THE INVENTION

The applicants have investigated to use a copper frame having excellentthermal conductivity (thermal expansion coefficient α=17×10⁻⁶/° C.) as alead frame for radiating heat generated at a semiconductor laser elementto outside of the package in developing a photo-electronic deviceintegrated with the semiconductor laser.

However, according to the structure, it has been found that exfoliationof an optical fiber is caused by a mounting test by solder reflow (10seconds at 260° C.)

In producing a photo-electronic device, a case is formed to embed aportion of a lead frame by transfer mold. A base plate (pad) comprisinga copper plate is formed at an inner bottom face of a case and a siliconsubstrate (thermal expansion α=3.0×10⁻⁶/° C.) is fixed onto the baseplate. A semiconductor laser element, a light receiving element, anoptical fiber and the like are fixed onto the silicon substrate. A frontend portion of an optical fiber is positioned to face an emitting faceof the semiconductor laser element and a front end portion thereof isadhered to the silicon substrate by an adhering agent. Further, aportion at a middle of the optical fiber is fixed to the case by anadhering agent.

Here, the optical fiber indicates also an optical fiber core line formedby a core and quartz covering the core and the optical fiber cablecovering the optical fiber core line by a cover member of a jacket. Whenthe optical fiber core line or the optical fiber cable may not bespecified particularly or may not preferably be specified, these arereferred to simply as optical fiber in the following.

When a constitution of supporting an optical fiber (optical fiber coreline) is constructed by two points support constitution of fixing afront end portion of the optical fiber and a middle portion thereof,tensile force is operated to the optical fiber core line by thermaldeformation of the base plate caused by heat in the solder mount testand the tensile force exceeds force of adhering the silicon substrateand the optical fiber core line and the optical fiber core line isexfoliated. Exfoliation of the optical fiber at the front end portion ofthe optical fiber causes a phenomenon in which a deterioration is causedin transmission and reception efficiency of light to and from thesemiconductor laser element or light is not inputted at all from thefront end.

In order to resolve such a problem, the applicants have investigated toform the lead frame by a material the thermal expansion coefficient ofwhich is proximate to that of silicon. As a material the thermalexpansion coefficient is proximate to that of silicon, there are kovar,42 alloy and the like. Hence, the applicants have formed the lead frameby 42 alloy (α=5×10⁻⁶/° C.). Therefore, the base plate and the leadintegrated to the case are made of 42 alloy. The thermal conductivity of42 alloy is as small as 13.4 W/m·k in comparison with 146 W/m·k of Cuand achieves an effect of capable of restraining temperature rise of thebase plate per se and restraining deformation of the base plate.Thereby, there is provided a structure in which the optical fiber isdifficult to exfoliate.

Meanwhile, the applicants have investigated also on adaptability ofresin constituting the case. Since the case is exposed to hightemperature even in a short period of time, as a resin constituting thecase, the resin having heat resistant temperature of 200° C. or higherhas been investigated. Although as resins, there are thermoplastic resinand thermosetting resin, thermoplastic resin is used since thermosettingresin is provided with a drawback in which the time period of moldingthereof is long and the resin is not reproducible. Thermoplastic resinis widely used as engineering plastic.

As resin having the heat resistant temperature equal to or higher than200° C., there are polyphenylene sulphide (PPS), polyether sulfone(PES), polyetherketone (PEEK) and liquid crystal polymer (LCP).

PES, PEEK and LCP are expensive and PPS is balanced in view of heatresistance and price.

Although the price is high, the liquid crystal polymer (LP) is featuredin high heat resistance (thermal deformation temperature equal to orhigher than 260° C.) and high bending strength (bending strength: 21.2kg/mm² at 25° C.). Further, the liquid crystal polymer is particularlyfeatured in small linear expansion coefficient in a direction of flow ofresin in molding thereof. The linear expansion coefficient of the resinin the flow direction is 2.0×10⁻⁶/° C. and the linear expansioncoefficient in a direction orthogonal to the flow is 66×10⁻⁶/° C.

Hence, the applicants have conceived to prevent breakage caused by thethermal stress of the optical fiber core line by molding the case bymaking the resin flow in the direction of extending the optical fibercore line and approximating the thermal expansion coefficient of thecase in the direction of extending the optical fiber core lane to thethermal expansion coefficient of the optical fiber core line.

However, in the case of the liquid crystal polymer, the thermalconductivity is as small as 0.4 W/m·k and the tensile strength of weldafter molding is smaller than 25 MPa in comparison with 55 MPa or moreof various engineering plastics. In order to improve the heat radiatingperformance, the thinner the resin thickness below the base plate fixedwith the semiconductor laser element, that is, the thickness of thebottom of the case, the more preferable. However, as mentioned above,the liquid crystal polymer is provided with the low tensile strength ofweld and the bottom of the case becomes brittle. Hence, the inventorshave conceived to increase the strength by partially thickening thebottom of the case.

Meanwhile, it has been found that there is a case of breaking theoptical fiber core line from the following reason by analysis andinvestigation by the inventors.

FIG. 21 is an enlarged sectional view showing a portion of a package 5of a photo-electronic device according to an investigation by theapplicants. The package 5 comprises a case 10 and a cap 11 adhered andfixed to overlap the case 10.

The case 10 comprises a case main body portion 10 a and a slender caseguide portion 10 b continuous to the case main body portion 10 a. Thecap 11 comprises a cap main body portion 11 a overlapping the case mainbody portion 10 a and a cap guide portion 11 b overlapping the caseguide portion 10 b.

The case main body 10 a is constituted by a box type structure the upperportion of which is opened and is constituted by a structure in which aplurality of leads, not illustrated, constituting external electrodeterminals are projected respectively from both sides thereof. A baseplate 15 comprising a metal plate is provided at an inner bottom of thecase main body portion 10 a and a support substrate (silicon platform,not illustrated) is fixed onto the base plate 15.

The support substrate is fixed respectively with a semiconductor laserelement, a light receiving element and a front end portion of an opticalfiber core line 3 a. Further, a gel-like resin 36 is filled in the casemain body portion 10 a for covering the semiconductor laser element, thelight receiving element and the optical fiber core line.

The case guide portion 10 b and the cap guide portion 11 b areconstructed by a structure of guiding an optical fiber cable and anoptical fiber core line which becomes bare by removing a jacket (covermember) of the optical fiber cable. That is, match faces of the caseguide portion 10 b and the cap guide portion 11 b are respectivelyprovided with grooves. The grooves comprise cable guide grooves forguiding the optical fiber cable and core line guide grooves 10 d and 11d continuous to the cable guide grooves. The cable guide grooves areextended from ends of the case guide portion 10 b and the cap guideportion 11 b to middle portions thereof and remaining portionsconstitute the core line guide grooves 10 d and 11 d. The optical fibercable is constructed by a structure of covering the optical fiber coreline 3 a comprising the core and the clad by a cover member (jacket).Therefore, the optical fiber cable integrated to the photo-electronicdevice is brought into a state of the optical fiber core line 3 a byremoving the jacket over a predetermined length at the front end side.

The case guide portion 10 b and the cap guide portion 11 b are insertedwith the portion of the optical fiber core line 3 a and the portion ofthe optical fiber cable and the portions are fixed to the case guideportion 10 b and the cap guide portion 10 b via an adhering agent 38.Further, the front end portion of the optical fiber core line 3 a isfixed to the silicon platform via an adhering agent.

It has been found that according to such a structure, there is a case inwhich optical transmission cannot be carried out by causing adisconnection failure of the optical fiber core line 3 a inserted intothe case guide portion 10 b and the cap guide portion 11 b.

The following has been found as a result of analyzing and investigatingthe point. That is, in forming the gel-like resin 36, silicone resinhaving fluidity is supplied to the case main body portion 10 a and thesilicone resin flows into a clearance between the outer peripheralportion of the optical fiber core line 3 a and the core line guidegroove 10 d. As a result, the gel-like resin 36 and the adhering agent38 are brought into contact with each other over a long distance in thecore line guide groove 10 d and 11 d.

The gel-like resin 36 uses the silicone resin and the adhering agent 38uses epoxy resin of amine species. Further, an adhering agent for fixingthe case 10 and the cap 11 also uses the epoxy resin of amine species.The epoxy resin of amine species is used since force thereof of adheringto the plastic case is excellent. However, adhering performance betweenthe gel-like silicone resin and the epoxy resin of amine species or theplastic case is not excellent.

As a result, it has been found that since the optical fiber is not fixedto the case guide portion, there causes a phenomenon in which tensilestress is operated to the optical fiber core line 3 a owing totemperature change and the optical fiber core line 3 a is broken.

Further, it has been also found that in the case in which moisture isstored at the interface 7, when the photo-electronic device is used in acold district, there causes a phenomenon in which the moisture stored atthe interface constitutes ice and the optical fiber core line is brokenby an increase in the volume. The breakage is particularly easy to occurwhen the interface is disposed at an area of the case guide portion 10 band the cap guide portion 11 b.

It is an object of the invention to provide a photo-electronic devicecapable of preventing an optical fiber from being broken and a method ofproducing thereof.

It is other object of the invention to provide a photo-electronic devicehaving high efficiency of optically coupling a photoelectric conversionelement and an optical fiber and a method of producing thereof.

It is other object of the invention to provide a photo-electronic devicehaving high heat radiating performance and a method of producingthereof.

The above-described and other objects and novel features of theinvention will become apparent from description of the specification andattached drawings.

A simple explanation will be given of an outline of representativeaspect of the invention disclosed in the application as follows.

(1) According to an aspect of the invention, there is provided aphoto-electronic device including a package having a main body portioncontaining parts including a photoelectric conversion element at insidethereof and a guide portion a front end of which faces the photoelectricconversion element for guiding, in a penetrated state, an optical fiberfor transmitting and receiving light to and from the photoelectricconversion element, in which the optical fiber is fixed to the guideportion by an adhering agent at the guide portion and portions of themain body portion including the photoelectric conversion element and afront end portion of the optical fiber are covered by a protective filmformed by a resin transparent to the light and a dam is provided betweenthe protective film and the adhering agent such that the protective filmand the adhering agent are not brought into contact with each other.

According to another aspect of the invention, there is provided thephoto-electronic device, wherein the package is formed by a case and acap adhered to overlap the case, the case is formed by a case main bodyportion and a case guide portion continuous to the case main bodyportion, the cap is formed by a cap main body portion and a cap guideportion continuous to the cap main body portion, the case main bodyportion is embedded with a predetermined shape of a metal plate aportion of which forms a base plate exposed to an inner bottom of themain body portion, remaining portions of which form a plurality of leadsextended to inside and outside of the main body portion, a supportsubstrate (silicon substrate: silicon platform) is fixed onto the baseplate and the photoelectric conversion element and the optical fiber fortransmitting and receiving light to and from the photoelectricconversion element are fixed onto the support base plate.

The support substrate is fixed with a semiconductor laser element, alight receiving element and the front end portion of the optical fiber,the optical fiber is positioned and fixed to input laser beam on oneside emitted from the semiconductor laser element from a front end to aninner portion thereof and the light receiving element is positioned andfixed to receive laser beam on other side emitted from the semiconductorlaser element. Further, the front end portion of the optical fiber isfixed to the support substrate by an ultraviolet ray cured adheringagent and is fixed to the support substrate by a thermosetting adheringagent.

The protective film is formed by a gel-like resin, the adhering agent isformed by epoxy resin of amine species and the dam is formed by anultraviolet ray cured adhering agent of epoxy resin species. Further,there is present an air gap at a portion of the main body portion abovethe protective film.

The metal plate forming the base plate or the leads is formed by 42alloy or kovar the thermal expansion coefficient of which is proximateto the thermal expansion coefficient of the support substrate or theoptical fiber and the case and the cap constituting the package areformed by a resin (liquid crystal polymer) in which the thermalexpansion coefficient in the direction along the flow of resin inmolding becomes smaller than the thermal expansion coefficient in adirection orthogonal to the flow direction and the case and the cap aremolded such that the thermal expansion coefficients in the direction ofextending the optical fiber are reduced.

A peripheral edge portion of a bottom of the case main body portion ofthe case formed by the resin, is projected to thicken more than an innerside portion thereof and at the center of the base plate, the resin isnot provided over a predetermined length along the direction ofextending the optical fiber and the rear face of the base plate isexposed. The peripheral edge portion of the bottom of the main bodyportion of the package is projected to thicken more than the inner sideportion.

Such a photo-electronic device is produced by the following method.

According to another aspect of the invention, there is provided a methodof producing a photo-electronic device in which a package is formed by acase and a cap adhered to overlap the case, the case is formed by a casemain body portion and a case guide portion continuous to the case mainbody portion, the cap is formed by a cap main body portion and a capguide portion continuous to the cap main body portion, the case mainbody portion is embedded with a predetermined shape of a metal plate aportion of which forms a base plate exposed to an inner bottom of thecase main body portion and remaining portions or which form a pluralityof leads extended to inside and outside of the case main body portion, asupport substrate (silicon substrate: silicon platform) is fixed ontothe base plate, a photoelectric conversion element an electrode of whichis connected electrically to the lead is fixed onto the supportsubstrate, an optical fiber is supported by the guide portion in apenetrated state and fixed thereto by an adhering agent, a front end ofthe optical fiber is fixed to the support substrate to transmit andreceive light to and from the photoelectric conversion element and aprotective film which is transparent to the light covers thephotoelectric conversion element and the optical fiber in the main bodyportion, the method comprising the steps of fixing the support substratefixed with the photoelectric conversion element to inside of the mainbody portion, fixing a front end portion of the optical fiber by anadhering agent,

forming the protective film by filling a resin in the main body portion,and fixing the optical fiber to the guide portion by an adhering agent,wherein a dam is formed at a boundary portion of the main body portionand the guide portion such that the protective film does not invade theguide portion prior to forming the protective film.

According to another aspect of the invention, there is provided themethod of producing a photo-electronic device wherein a semiconductorlaser element is fixed to the support substrate, the front end portionof the optical fiber is positioned and fixed such that laser beam on oneside emitted from the semiconductor laser element is inputted from afront end thereof to an inner portion thereof and a light receivingelement is positioned and fixed to receive the laser beam on other sideemitted from the semiconductor laser element. After optical coupleadjustment of the optical fiber, the front end portion of the opticalfiber is coupled by the ultraviolet ray cured adhering agent and isfixed thereto by the thermosetting adhering agent.

The case is formed by fastening a lead frame to mold dies of transfermold and thereafter molding liquid crystal polymer resin to flow fromone end portion to other end portion of the case and cutting andremoving an unnecessary portion of the lead frame. In the transfer mold,the molding operation is carried out by pressing a portion of the leadframe constituting the base plate to a mold upper die by a pressure pin,the pressure pin is extended over a predetermined length along thedirection of extending the optical fiber at the center of the baseplate, the flowing resin is divided at one end side of the pressure pinand flows along both sides of the pressure pin and thereafter mergesagain on other end side of the pressure pin to flow. The case main bodyportion of the case is molded such that the resin thickness at theperipheral edge of the bottom thereof is thickened. The lead frame isformed by 42 alloy or kovar.

The protective film is formed by a gel-like resin which is transparentto the light, the adhering agent for fixing the optical fiber to thecase guide portion is formed by epoxy resin of amine species and the damis formed by an ultraviolet ray cured adhering agent of epoxy resinspecies.

According to the means of (1):

(a) Since the dam is present, the silicone resin does not flow out tothe case guide portion by riding over the dam. Therefore, the epoxyresin of amine species having poor adhering performance with thesilicone resin, is not brought into contact with the silicone resin, thecase guide portion is filled with the epoxy resin of amine species, theforce of adhering the case and the cap is also maintained andaccordingly, the fiber can firmly be fixed, thermal stress caused bythermal variation is difficult to apply to the optical fiber (opticalfiber core line), the optical fiber core line is difficult to break andoptical transmission failure is difficult to cause.

(b) The thermal expansion coefficient of the case and the cap in thedirection of extending the optical fiber is 4.0×10⁻⁴/° C. (liquidcrystal polymer), the thermal expansion coefficient of the base platecomprising 42 alloy is 5×10⁻⁶/° C., the thermal expansion coefficient ofthe silicon platform is 3.0×10⁻⁶/° C., the thermal expansion coefficientof the optical fiber core line is 0.5×10⁻⁶/° C., all of the coefficientsare smaller than that of copper (a=17×10⁻⁶/° C.) and are provided withnumerical values proximate to each other and therefore, it is difficultto cause exfoliation of the optical fiber fixed by the silicon platformand the case guide portion owing to deformation of the base plate.Further, the front end portion of the optical fiber is fixed to thesupport substrate respectively by the ultraviolet ray cured adheringagent and the thermosetting adhering agent and accordingly, the adheringstrength is high and exfoliation of the optical fiber is difficult tocause. As a result, at the front end of the optical fiber, adeterioration in the transmission and reception efficiency of lightbetween the front end and the semiconductor laser element, is not causedand the optical fiber (optical fiber core line) is difficult to break atthe case guide portion.

(c) Liquid crystal polymer (LCP) is featured in high thermal resistance(thermal deformation temperature equal to or higher than 260° C.) andhigh bending strength (bending strength: 21.1 kg/mm² at 25° C.),however, the tensile strength of weld after molding is small. Therefore,when the resin thickness (liquid crystal polymer thickness) below thebase plate is thinned in order to improve heat radiating performance,the resin becomes brittle and easy to break, however, increase in thestrength is achieved by thickening the peripheral edge of the bottom ofthe case and accordingly, there is constituted the package having highreliability of mechanical strength.

(d) Since the air gap is present at an upper portion of the protectivefilm, even when the protective film is expanded by heat, the expandedportion elongates only to the air gap portion and is not brought intocontact with the cap on the upper side and accordingly, stress is notapplied to the optical fiber by deforming the package and the opticalfiber is difficult to break.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plane view showing a structure of preventingcontact between gel-like resin and amine species epoxy resin by a dam ina photo-electronic device according to an embodiment (Embodiment 1) ofthe invention;

FIG. 2 is a front view of the photo-electronic device according toEmbodiment 1;

FIG. 3 is a plane view of the photo-electronic device according toEmbodiment 1;

FIG. 4 is a side view of the photo-electronic device according toEmbodiment 1;

FIG. 5 is a schematic view showing pin layout of the photo-electronicdevice according to Embodiment 1;

FIG. 6 is an enlarged sectional view of the photo-electronic deviceaccording to Embodiment 1 along a direction of extending an opticalfiber;

FIG. 7 is an enlarged plane view in a state of removing a cap of thephoto-electronic device according to Embodiment 1;

FIG. 8 is an enlarged bottom view showing a portion of thephoto-electronic device according to Embodiment 1;

FIG. 9 is an enlarged sectional view showing a portion of thephoto-electronic device according to Embodiment 1;

FIG. 10 is an enlarged plane view of a silicon substrate portion in thephoto-electronic device according to Embodiment 1;

FIG. 11 is a plane view showing a case formed at a lead frame inproducing the photo-electronic device according to Embodiment 1;

FIG. 12 is a bottom view showing the case formed at the lead frame;

FIG. 13 is a sectional view enlarging a portion of the case formed atthe lead frame;

FIG. 14 is a sectional view showing a state of forming the case by atransfer mold process;

FIG. 15 is a perspective view enlarging a portion of the case;

FIG. 16 is a perspective view of a portion showing a state of attachingan optical fiber to the case in producing the photo-electronic deviceaccording to Embodiment 1;

FIG. 17 is a schematic view showing a state of positioning an opticalfiber core line to the silicon substrate in producing thephoto-electronic device according to Embodiment 1;

FIGS. 18A through 18C are schematic views showing a method of fixing theoptical fiber core line to the silicon substrate;

FIG. 19 is a schematic perspective view showing a state of tacking theoptical fiber to a groove;

FIG. 20 is an enlarged sectional view showing a state of puttingsilicone gel into the case in producing the photo-electronic deviceaccording to Embodiment 1; and

FIG. 21 is a sectional view enlarging a portion of a photo-electronicdevice by investigation by the applicant.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A detailed explanation will be given of embodiments of the invention inreference to the drawings as follows. Further, in all the drawings orexplaining embodiments of the invention, portions having the samefunctions are attached with the same notations and a repetitiveexplanation thereof will be omitted.

(Embodiment 1)

FIG. 1 through FIG. 20 are views related to a photo-electronic deviceand a method of producing thereof according to an embodiment(Embodiment 1) of the invention.

As shown by FIG. 2 and FIG. 3, a photo-electronic device (semiconductoroptical module) 1 according to Embodiment 1, comprises a module mainbody 2 and an optical connector 4 attached to a front end of an opticalfiber cable 3 constituting the module main body 2 in its outlook.

The module main body 2 comprises the package 5 having a flatparellelepiped structure, the optical fiber cable 3 projected from oneend of the package 5 and leads 6 constituting a plurality of externalelectrode terminals projected to align from both sides of the package 5.As shown by FIG. 4, according to Embodiment 1, the leads 6 are formed indual in line type. According to Embodiment 1, there is constructed astructure in which four pieces of the leads 6 are respectively projectedfrom the both sides of the package 5.

FIG. 5 is a schematic view showing layout of the leads 6. Asemiconductor laser element (laser diode: LD) and a light receivingelement (photodiode: PD) are integrated In the package 2. In FIG. 5,numerals 1 through 8 are attached to the leads 6. The leads of 1, 3, 8are NC pins not connected, the lead of 2 is a package ground pin, thelead of 4 is a cathode pin of a photodiode, the lead of 5 is an anodepin of the photodiode, the lead of 6 is a cathode pin of the laser diodeand the lead of 7 is an anode pin of the laser diode.

Therefore, when predetermined voltage is applied across the leads of 6and 7, the laser diode emits laser beam. The laser beam is transmittedto outside of the package 5 by the optical fiber cable 3 and istransmitted to an optical fiber cable, not illustrated, connected by theoptical connector 4.

The package 5 is formed by a case 10 made of plastic (resin) and a cap11 made of plastics fixed onto the case 10. The case 10 is constitutedby a case main body portion 10 a in a rectangular shape and a case guideportion 10 b projected from center of one end of the case main bodyportion 10 a in a slender shape and the cap 11 is constituted by a capmain body portion 11 a in a rectangular shape and a cap guide portion 11b projected from center of one end of the cap main body portion 11 a ina slender shape. Therefore, when the cap 11 is adhered to fix to thecase 10, a main body portion thereof is formed by the case main bodyportion 10 a and the cap main body portion 11 a and a guide portionthereof is formed by the case guide portion 10 b and the cap guideportion 11 b. The case 10 and the cap 11 are formed by liquid crystalpolymer comprising insulating resin.

The semiconductor laser element and the light receiving element arearranged in the case main body portion 10 a. Further, the guide portion,that is, the case guide portion 10 b and the cap guide portion 11 b, inthe adhered state, are constructed by a structure for guiding, in apenetrated state, an optical fiber cable and an optical fiber core line(comprising a clad and a core penetrating center of the clad) whichbecomes bare by removing a jacket (cover member) of the optical fibercable. A portion of the optical fiber cable 3 projected from the caseguide portion 10 b and the cap guide portion 11 b, is fixed by anadhering agent 12. The adhering agent 12 is for tacking the opticalfiber cable 3 to the case guide portion 10 b.

Next, an explanation will be given of the module main body 2 inreference to FIG. 1 and FIG. 6 through FIG. 10. FIG. 6 is an enlargedsectional view of the module main body 2 along a direction of extendingthe optical fiber, FIG. 7 is an enlarged plane view of the module mainbody 2 in a state of removing the cap 11 and FIG. 8 is a bottom viewthereof. Further, FIG. 9 is an enlarged sectional view showing astructure of supporting the optical fiber core line at a boundaryportion of the case main body portion 10 a and the case guide portion 10b and FIG. 10 is an enlarged plane view showing a support substrate andoptical parts fixed to the support substrate.

As shown by FIG. 6 and FIG. 7, a base plate 15 comprising a metal plateis provided at an inner bottom of the case main body portion 10 a.Further, inner ends of the leads 6 are respectively disposed at asurrounding of the base plate 15. The base plate 15 and the leads 6 areintegrated to the case 10 in molding the case 10.

The optical fiber cable 3 is guided to the case guide portion 10 b and asupport substrate 16 comprising a silicon substrate generally referredto as silicon platform, is fixed over the base plate 15 on an extensionline of the optical fiber axis of the optical fiber cable 3 by a bondingmember 17, for example, silver paste.

The optical fiber cable 3 is covered wish a cover member (jacket) madeof nylon. Although the cover member is present up to a middle of thecase guide portion 10 b of the case 10, at a front end side thereof, thecover member is stripped and an optical fiber core line 3 a comprisingthe core and the clad is exposed. As shown by FIG. 10, the portion ofthe optical fiber core line 3 a is fitted to creep in a groove 20provided at the support substrate (silicon platform) 16. Further, thereis constructed a structure in which a semiconductor laser element(semiconductor laser chip) 21 as a photoelectric conversion element anda light receiving element (photodiode) 22 are fixed to align in seriesonto the silicon platform 16 on an extension thereof.

Laser beam (one laser beam) emitted from one emitting face of thesemiconductor laser element 21 is inputted into the optical fiber from afront end of the optical fiber core line 3 a and laser beam (other laserbeam) emitted from other emitting face thereof is received by the lightreceiving element 22 to monitor an optical output intensity.

As shown by FIG. 10, one face of the silicon platform 16 is providedwith patterned conductive metallized layers 25. The metallized layers 25constitute bonding pads for connecting mounting portions for mountingthe semiconductor laser element 21 and the light receiving element 22 orconductive wires. Further, the semiconductor laser element 21 and thelight receiving element 22 are fixed onto the mounting portions viaconductive adhering layers. Both of the semiconductor laser element 21and the light receiving element 22 are provided with electrodes at upperfaces and lower faces thereof and accordingly, the lower electrodes arerespectively connected electrically to the predetermined metallizedlayers 25.

As shown by FIG. 6 and FIG. 7, portions of the metallized layerscontinuous to the mounting portions and inner end portions of thepredetermined leads 6 are connected by conductive wires 26. Further, theA upper face electrodes of the semiconductor laser element 21 and thelight receiving element 22 are fixed to the metallized layersindependent from each other respectively via the conductive wires 26 andportions of the metallized layers are electrically connected to theinner end portions of the predetermined leads 6 via the wires 26.

Further, there is provided a discharge groove 27 to intersect the groove20 provided at the one face of the silicon platform 16 (refer to FIG.10). Although the optical fiber core line 3 a (optical fiber) is broughtinto a state of passing over the discharge groove 27, a length of theoptical fiber core line 3 a which passes over the discharge groove 27and projected, is extremely short. For example, the projected length isabout 100 μm. Further, the diameter of the optical fiber core line 3 a,that is, the diameter of the clad is, for example, about 125 μm.

As shown by FIG. 10, at a vicinity of the discharge groove 27, theoptical fiber core line 3 a is fixed to the silicon platform 16 byfixing by two kinds of adhering agents of a primary fixing portion 30and a secondary fixing portion 31. The primary fixing portion 30 isconstituted by an ultraviolet ray cured adhering agent and the secondaryfixing portion 31 is constituted by a thermosetting resin.

As shown by FIG. 10, the primary fixing portion 30 is formed in aslender shape along the optical axis of the optical fiber core line 3 a.The optical fiber core line 3 a is inserted and positioned to creep inthe groove 20, thereafter, the ultraviolet ray cured adhering agent iscoated and thereafter, ultraviolet ray is irradiated to cure theultraviolet ray cured adhering agent and carry out primary fixing(tacking). The optical fiber core line 3 a is firmly fixed to thesilicon platform 16 by the primary fixing. Therefore, thereafter, thereis carried out secondary fixing constituting full fixing. The secondaryfixing is carried out by coating the thermosetting resin at a portion ofthe optical fiber fixed by the primary fixing portion 30 remote from thesemiconductor laser element 21 and curing the resin thereafter. Thesecondary fixing processing can be carried out in batch and theproductivity can be promoted.

In the primary fixing processing and the secondary fixing processing, asa standard, adhering agents of the ultraviolet ray cured adhering agentand the thermosetting resin are coated not to ride over the dischargegroove 27. The adhering agent which enters the discharge groove 27 isguided to side portions of the silicon platform 16 via the dischargegroove 27 and accordingly, the adhering agent does not enter between thefront end face of the optical fiber core line 3 a and the emitting faceof the semiconductor laser element 21 and transmission and reception oflight is not hampered.

Meanwhile, a gel-like resin showing a rubber characteristic is filled inthe case main body portion 10 a to thereby form a protective film 36.The protective film 36 is a protective member which is not onlytransparent to the laser beam to prevent transmission loss of the laserbeam which is emitted from the semiconductor laser element 21 andreaches the front end of the optical fiber core line 3 a but alsoexcellent in humidity resistance. The protective film 36 covers the baseplate 15, the silicon platform 16, the optical fiber core line 3 a, thesemiconductor laser element 21 and the light receiving element 22 tothereby achieve promotion of humidity resistance of the semiconductorlaser element 21 and the light receiving element 22.

On the other hand, as shown by FIG. 1, FIG. 6 and FIG. 7, there arerespectively provided grooves at match faces of the case guide portion10 b and the cap guide portion 11 b. The grooves comprise cable guidegrooves 10 c and 11 c for guiding the optical fiber cable 3 and coreline guide grooves 10 d and 11 d continuous to the cable guide grooves10 c and 11 c. The cable guide grooves 10 c and 11 c are extended fromends to middles of the case guide portion 10 b and the cap guide portion11 b and remaining portions thereof constitute the core line guideportions 10 d and 11 d. The cable guide grooves 10 c and 11 c areprovided with grooves 10 e and 11 e in the peripheral direction in orderto increase strength of fixing the optical fiber cable 3 by filling theresin by a larger amount.

Further, as one of characteristics of the invention, there is formed adam 35 by resin at front end portions (inner end portions) of the coreline guide grooves 10 d and 11 d on the side of the semiconductor laserelement 21. The dam 35 is formed by dripping of resin and processing tocure thereof to fill up an outer peripheral clearance of the opticalfiber core lines 3 a inserted into the cores line guide grooves 10 d and11 d and serves as a dam for preventing silicone resin filled in thecase main body portion 10 a from invading the case guide portion 10 band the cap guide portion 11 b via the outer peripheral clearance of theoptical fiber core line 3 a in filling thereof.

In order to promote the dam effect, there is adopted a structure inwhich an inner end of the core line guide groove 10 d is projected tothe center side of the case main body portion longer than the core lineguide groove 11 d. Therefore, in dripping the resin when the dam 35 isformed, the resin is mounted also on the projected portion 37 and asshown by FIG. 9, there is formed the dam 35 which is slightly elevatedand in filling the resin for forming the protective film 36, the resincan be prevented from invading.

Adhering agents 38 and 42 are filled in the core line guide grooves 10 dand 11 d and the cable guide grooves 10 c and 11 c outward from theprotective film 36 to thereby fix the optical fiber core line 3 a andthe optical fiber cable 3.

The protective film 36 is formed by, for example, transparent siliconeresin capable of transmitting laser beam (α=4.0×10⁻⁴/° C.). The adheringagents 38 and 42 are formed by amine species epoxy resin. The dam 35 isused for separating the protective film 36 and the adhering agents 38and 42 comprising the amine species epoxy resin. For example, the dam 35is formed by, for example, an ultraviolet ray cured adhering agent ofepoxy resin species (α=6.2×10⁻⁵/° C.)

Further, the protective film 36 is not limited to silicone gel but maybe formed by silicone rubber, low stress epoxy resin, acrylic resin orurethane resin any of which is transparent.

Since the dam 35 is present in this way, the protective film 36comprising the gel-like resin provided at the main body portion, is notbrought into contact with the adhering agent 38 for fixing the opticalfiber to the guide portion and accordingly, thermal stress caused bythermal variation becomes difficult to apply to the optical fiber coreline, breakage of the optical fiber core line is difficult to cause andfailure in optical transmission is difficult to cause.

The resin for forming the dam 35 comprises epoxy resin of an ultravioletray cured type and therefore, the resin can be cured by steps the sameas the steps of irradiating ultraviolet ray in fixing the optical fiberto the silicon substrate.

The amine species epoxy resin is used for the adhering agents 38 and 42by the following reason. That is, the adhering force for adhering to aplastic case is excellent. The kind of the adhering agent is not limitedso far as the force of adhering to the plastic case can be maintained.

FIG. 1 is a plane view of the photo-electronic device 1 in a statebefore attaching the cap 11 to the case 10. According to the drawing, astate in which the protective film 36 and the adhering agent 38 are notbrought into direct contact with each other by the presence of the dam35, is apparent. Further, FIG. 7 is illustrated by removing a portion ofthe protective film 36.

Further, the case 10 is fixed with the cap 11 by the adhering agent 42.Epoxy resin of amine species having a material the same as that of theadhering agent 38 is used for the adhering agent. At the case guideportion 10 b and the cap guide portion 11 b, the adhering agent 42overlaps the adhering agent 38.

According to Embodiment 1, the base plate 15 and the leads 6 integratedto the case 10, are formed by 42 alloy having thermal expansioncoefficient (α=5×10⁻⁶/° C.) proximate to thermal expansion coefficientof silicon (α=3.0×10⁻⁶/° C.) or quartz (α=0.5×10⁻⁶/° C.) constitutingthe optical fiber core line 3 a and the case 10 and the cap 11 formed bytransfer mold, are formed by anisotropic liquid crystal polymer. Thatis, thermal expansion coefficient of the liquid crystal polymer in adirection of flow of resin in transfer mold, s as small as 2.2×10⁻⁶/° C.and is proximate to the thermal expansion coefficient of silicon orquartz. Hence, the case 10 is formed to make resin flow along thedirection of extending the optical fiber. FIG. 8 shows a gate mark 40 intransfer mold and flow of resin in transfer mold (indicated by arrowmarks). In transfer mold, a pressure pin is brought into contact with arear face side of the base plate 15 and therefore, after transfer mold,the base plate 15 is exposed as shown by FIG. 8, the exposed portionbecomes a slender region and is provided with a wide area andaccordingly, heat radiating performance is further improved.

The case 10 and the cap 11 are formed by the liquid crystal polymer, thebase plate 15 is formed by 42 alloy, the thermal expansion coefficientsof the package 5 and the base plate 15 in the direction of extendingoptical fiber, are proximate to the thermal expansion coefficient of theoptical fiber core line and accordingly, the optical fiber core lineportion fixed to the silicon platform 16 fixed to the base plate 15 andthe optical fiber core line portion fixed to the case guide portion 10 band the cap guide portion 11 b are difficult to exfoliate by heat inmounting the photo-electronic device 1 and a deterioration in anefficiency of optically coupling the semiconductor laser element 21 andthe optical fiber core line 3 a, is difficult to cause. Further, it isdifficult to cause disconnection failure of the optical fiber core line3 a which is caused since the optical fiber core line 3 a is not fixed.

Although according to Embodiment 1, by thinning the thickness of thecase 10 below the base plate 15 (for example, 0.25 mm) to therebyincrease an effect of irradiating heat to the atmosphere, as mentionedabove, tensile strength of weld of liquid crystal polymer is low.Therefore, when the thickness of the liquid crystal polymer at thebottom or the case 10 is thinned, the case 10 becomes brittle and themechanical strength is reduced and therefore, as shown by FIG. 6, FIG. 8and FIG. 9 (refer to FIG. 13), ribs 41 are formed by thickeningperipheral edge portions. For the purpose of reinforcement to promotethe strength, there may be constructed not only the structure of onlythickening the peripheral edge in this way but also a structure ofpartially thickening hereof or a structure of providing a plurality ofthick portions.

Thereby, the mechanical strength of the package 5 can be promoted, thereliability of the package can be promoted and long life of thephoto-electronic device 1 can be achieved.

Next, an explanation will be given of a method of producing thephoto-electronic device (semiconductor optical module) 1.

At first, respective parts or assembled articles are prepared. That is,there are prepared the case 10 made of plastics with guide for guidingthe optical fiber and the cap 11 made of plastics attached to close thecase 10, the silicon platform 16 mounted with the semiconductor laserelement 21 and the light receiving element 22 at the one face and havingthe groove 20 extended toward the semiconductor laser element 21 and soon. The case 10 and the cap 11 are provided with the above-describedstructures.

Although as described above, the silicon platform 16 is fixed with thesemiconductor laser element 21 and the light receiving element 22 asshown by FIG. 10, at this stage, the silicon platform 16 is not fixedwith the optical fiber core line 3 a and connection by the wires 26 isnot carried out.

Here, an explanation will be given of the method of producing the resincase 10 having the leads. FIG. 11 is a plane view of forming the case 10at a lead frame 50 by the transfer mold process, FIG. 12 a bottom viewthereof and FIG. 13 is a sectional view thereof. Further, FIG. 14 is asectional view showing a state of carrying out transfer mold byfastening the lead frame by a lower mold die and an upper mold die.

The lead frame 50 is formed by 42 alloy in place of copper toapproximate the thermal expansion coefficient to that of silicon. Kovarmay be use in place of 42 alloy. Although not particularly restricted,there is used the lead frame 50 having the thickness of 0.25 mm. Asshown by FIG. 11, the lead frame 50 is provided with a frame 53 of thelead frame having a frame structure comprising a pair of outer frames 51extended in parallel with each other and a pair of inner frames 52extended in parallel with each other orthogonally to the outer frames51.

Four pieces of the leads 6 are extended in parallel with the outerframes 51 at predetermined intervals from an inner side of a left halfof each of the pair of inner frames 52. There is constructed a patternin which at least one piece of the leads 6 extended from the inner frame52 is connected to the base plate 15 at the center. The lead 6 connectedto the base plate 15 constitutes package ground. There is constructed apattern in which front ends of the remaining leads 6 face vicinities ofthe base plate 15. In FIG. 11, four pieces of the leads 6 arerespectively projected from the inner frame 52.

The four pieces of leads 6 aligned in parallel are connected by a dampiece 54. The dam piece 54 constitutes a pattern along the outerperiphery of the case 10, is made slender at a portion of the fourpieces of leads 6 on the left side and expanded to the center side onthe left side to thereby constitute a wide width. The case main bodyportion 10 a is formed at the left side portion and the case guideportion 10 b is formed on the right side. The case main body portion 10a is constructed by a box shape structure the upper portion of which isopened and the case guide portion 10 b is provided with the slender coreline guide groove 10 d for guiding the optical fiber core line and thecable guide groove 10 c linearly continuous to the core line guidegroove 10 d. The cable guide groove 10 c is provided with the grooves 10e.

Further, as shown by FIG. 15, the projected portion 37 is provided on aninner end side of the core line guide groove 10 d and the portionconstitutes a portion of forming the dam 35. Therefore, when the dam 35is formed by potting and curing the resin over the projected portion 37(refer to FIG. 1 and FIG. 6), an opening portion 55 for filling theprotective film 36 of the case main body portion 10 a and the core lineguide groove 10 d of the case guide portion 10 b are separated by thedam 35.

A width at a portion of the lead 6 projected from the case main bodyportion 10 a is wide and becomes slender at a middle thereof. The dampiece 54 is provided at a bold portion of the lead. Further, the frame53 for the lead frame is provided with guide holes 57 and 58 used fortransferring or positioning the lead frame 50.

In transfer mold, as shown by FIG. 14, the lead frame 50 is fastened bya mold lower die 61 and a mold upper die 62, liquid crystal polymer 64in a liquid state is injected from a gate 63 provided at the left endportion into the cavity formed by the mold lower die 61 and the moldupper die 62 to thereby form the case 10.

In the transfer mold, the base plate 15 of the lead frame 50 iselastically pressed to the mold upper die 62 by a pressure pin 65integrated to the mold lower die 61. Thereby, the liquid crystal polymer64 in the liquid state is prevented from moving around to a side of amounting face of the support plate 15 for fixing the semiconductor laserelement and the like.

FIG. 12 is the bottom view of forming the case 10 to the lead frame 50by the transfer mold process and a round portion remaining at the bottomface of the case main body portion 10 a is the gate mark 40. Further, anexposed region of the base plate 15 is a region with which the pressurepin 65 has been brought into contact. The arrow marks shown in thedrawing indicate a state of flow of the liquid crystal polymer 64 in theliquid state in the cavity. As is apparent from the drawing, thedirection of flow of the liquid crystal polymer 64 in the liquid stateis directed along the direction of extending the optical fiber andtherefore, thermal expansion coefficient of the produced case 10 in thedirection of extending the optical fiber becomes as small as 2.0×10⁻⁶/°C. or a numerical value proximate to that of the silicon substrate.Although an explanation will be omitted here, the cap 11 is producedalso by the liquid crystal polymer and is formed such that the thermalexpansion coefficient in a direction along the direction of extendingthe optical fiber becomes as small as 2.0×10⁻⁶/° C.

According to Embodiment 1, the slender pressure pin 65 is disposed alongthe center of the rear face of the base plate 15 and accordingly, thereis not produced so-to-speak weld line formed by bringing portions of theresin in contact with each other at the region in contact with thepressure pin 65. As a result, there is no occurrence of crack caused bythe weld line and production yield of the case with the leads ispromoted.

Further, in molding the case 10 by the transfer mold, the thickness ofthe case 10 below the base plate 15 is thinned (for example, 0.25 mm) tothereby increase the effect of irradiating heat to the atmosphere,however, as described above, the liquid crystal polymer is provided withlow tensile strength of weld and therefore, as shown by FIG. 13, themechanical strength is increased by thickly forming the ribs 41 at thebottom peripheral edge of the case 10. Thereby, the mechanical strengthof the package 5 can be increased, reliability of the package can beincreased and long service life of the photo-electronic device 1 can beachieved.

Next, by cutting and removing the dam piece 54 connecting the respectiveleads 6 and cutting outer end portion of the leads 6 and separating theleads 6 from the inner frames 52, there can be fabricated the case of aso-to-speak butterfly type in which the leads 6 are extended straightlyin the transverse direction from the case 10. Further, there can beconstituted the dual in line type as shown by FIG. 4 by forming theleads 6 and bending thereof in the same direction simultaneously withcutting and separating the leads 6 or separately.

Next, an explanation will be given of assembling of the photo-electronicdevice by using the case 10 and the cap 11.

As shown by FIG. 17, the silicon platform 16 fixed with thesemiconductor laser element 21 and the light receiving element 22, ispositioned and fixed onto the base plate 15 disposed at the inner bottomof the case 10 via the bonding member 17. Further, although notillustrated, the upper electrodes of the semiconductor laser element 21and the light receiving element 22 and predetermined portions areconnected by the wires 26.

Next, as shown by FIG. 16, the optical fiber cable 3 is inserted intothe cable guide groove 10 c of the case guide portion 10 b and theoptical fiber core line 3 a on the front end side is inserted into thecore line guide groove 10 d. Further, as shown by FIG. 17, the front endof the optical fiber core line 3 a is made to face the emitting face ofthe semiconductor laser element 21 and is positioned and fixed to thesilicon platform 16 highly accurately by a passive alignment method byusing a mark, not illustrated, provided at the silicon platform 16.

Further, the positioning and fixing operation may be carried out by amethod in which predetermined potential is applied between predeterminedones of the leads 6 to thereby operate the semiconductor laser element21 to emit laser beam, the emitted beam is inputted from the front endof the optical fiber core line 3 a into the optical fiber and opticalcouple adjustment is carried out while detecting optical output tothereby fix the front end of the optical fiber core line 3 a.

The fixing operation is carried out by a method shown by, for example,FIGS. 18A through 18C. That is, as shown by FIG. 18A, after coating anultraviolet ray cured adhering agent 30 a in the groove 20 of thesilicon platform 16, the optical fiber core line 3 a is pressed to thebottom of the groove 20 by pressing thereof to the ultraviolet ray curedadhering agent 30 a. As shown by FIG. 18B, the pressing operation iscarried out by applying predetermined load to a press piece 66. Forexample, a load of 100 g is applied.

Next, the ultraviolet ray cured adhering agent 30 a on both sides of theoptical fiber core line 3 a is irradiated with ultraviolet ray by usingultraviolet ray irradiating fibers 67 and 68 to thereby cure theultraviolet ray cured adhering agent 30 a. The primary fixing portion 30is formed by the ultraviolet ray cured adhering agent 30 a cured therebyand the optical fiber core line 3 a is fixed to the silicon platform 16without moving.

Next, as shown by FIG. 18C, thermosetting resin 31 a is coated fromabove the optical fiber core line 3 a to extend to the one face of thesilicon platform 16 and subjected to a thermal curing processing tothereby form the secondary fixing portion 31 by the thermosetting resin31 a. Thereby, the optical fiber core line 3 a is highly accuratelyfixed to the silicon platform 16.

Next, as shown by FIG. 19, by fixing a portion of the optical fibercable 3 protected from the case guide portion 10 b by the ultravioletray cured adhering agent 12 of epoxy resin species and filling theultraviolet ray cured adhering agent of epoxy resin species in a portionof the core line guide groove 10 d at the projected portion 37 andcuring thereof, the dam 35 is formed. The dam 35 is for preventingsilicone resin from flowing toward the center side of the case guideportion 10 b via a clearance between the core line guide groove 10 d andthe optical fiber core line 3 a when the silicone resin is injected intothe case main body portion 10 a and preventing the silicone resin frombeing brought into contact with an adhering agent (epoxy resin of aminespecies) for fixing the optical fiber cable 3 and the optical fiber coreline 3 a at later steps.

Next, as shown by FIG. 20, the silicone resin is filled in the case mainbody portion 10 a. After filling the silicone resin, ultraviolet ray isirradiated, successively, heating and ageing (30 minutes at 120° C.) andheating and curing (1 hour at 120° C.) are carried out and theprotective film 36 is formed by the gel-like resin.

Next, the core line guide groove 10 d and the cable guide 10 c reachingthe adhering agent 12 from the dam 35, are coated and filled with epoxyresin of amine species and the resin is baked to thereby fix the opticalfiber cable 3 and the optical fiber core line 3 a to the case guideportion 10 b by the adhering agent 38 as shown by FIG. 1.

Next, the cap 11 is made to overlap the case 10, the both members areadhered to each other by the adhering agent 42 (epoxy resin of aminespecies) to thereby produce the photo-electronic device (semiconductoroptical module) 1 as shown by FIG. 6 and FIG. 2 through FIG. 4.

According to Embodiment 1, the following effects are achieved.

(1) Since the dam 35 is present, the protective film 36 comprising thegel-like resin provided at the main body portion and the adhering agent38 for fixing the optical fiber (optical fiber core line 3 a and opticalfiber cable 3) to the guide portion are not brought into contact witheach other. The resin forming the dam 35 comprises epoxy resin ofultraviolet ray cured type. Thereby, the case guide portion is filledwith the epoxy resin of amine species, the adhering force adhering thecase and the cap is maintained and accordingly, the fiber can be fixedfirmly, thermal stress caused by thermal variation is difficult to applyto the optical fiber (optical fiber core line), the optical fiber coreline is difficult to break and optical transmission failure is difficultto cause.

(2) The thermal expansion coefficient of the case 10 and the cap 11 inthe direction of extending the optical fiber (optical fiber core line 3a) is 4.0×10⁻⁴/° C. (liquid crystal polymer), the thermal coefficient ofthe base plate 15 made of 42 alloy is 5×10⁻⁶/° C., the thermal expansioncoefficient of the silicon platform 16 is 3.0×10⁻⁶/° C., the thermalexpansion coefficient of the optical fiber core line 3 a is 0.5×10⁻⁶/°C. and all of the thermal expansion coefficients are smaller than thatof copper (α=17×10⁻⁶/° C.) and are numerical values proximate to eachother and accordingly, it is difficult to cause exfoliation caused bythermal variation of the optical fiber fixed by the silicon platform andthe case guide portion. Further, the front end portion of the opticalfiber is fixed to the support substrate respectively by the ultravioletray cured adhering agent and the thermosetting adhering agent andaccordingly, adhering strength is high and exfoliation of the opticalfiber is difficult to cause. As a result, at the front end of theoptical fiber, a deterioration in the transmission and receptionefficiency of light between the front end of the optical fiber and thesemiconductor laser element is not caused and the optical fiber (opticalfiber core line) at the case guide portion is difficult to break.

(3) Although liquid crystal polymer (LCP) is featured in providing highheat resistance (thermal deformation temperature equal to or higher than260° C.) and high bending strength (bending strength: 21.1 kg/mm² at 25°C.), the tensile strength of weld after molding is small. Therefore,when the resin thickness (liquid crystal polymer thickness) below thebase plate is thinned to improve heat radiating performance, the resinbecome brittle and is easy to break, however, increase in the strengthis achieved by thickening the peripheral edge of the bottom of the caseand accordingly, there is constituted the package having highreliability of mechanical strength.

(d) Since an air gap is present above the protective film, even when theprotective film is expanded by heat, the expanded portion is onlyelongated into the air gap portion and is not brought into contact withthe cap on the upper side and accordingly, the optical fiber is notapplied with stress by deforming the package and the optical fiber isdifficult to break.

Although a specific explanation has been given of the invention carriedout by the inventors based on the embodiment as described above, theinvention is not limited to the above-described embodiment and cannaturally be modified variously within a range not deviated from gistthereof. That is, even in the case of a structure of connecting a lightreceiving element as a photoelectric conversion element and an opticalfiber, the invention is similarly applicable and can achieve a similareffect.

A simple explanation will be given of effects achieved by representativeaspects of the invention disclosed in the application as follows.

(1) The adhering agent comprising epoxy resin of amine species forfixing the optical fiber core line and the protective film comprisingthe gel-like resin are not brought into direct contact with each other,the dam comprising ultraviolet ray cured adhering agent is providedtherebetween and accordingly, a case guide portion is filled with epoxyresin of amine species and accordingly, breakage of the optical fibercore line by thermal stress can be prevented.

(2) Although the optical fiber (optical fiber core line) is constructedby a constitution of two points support, the case is formed by liquidcrystal polymer, the thermal expansion coefficient in the direction ofextending the optical fiber is reduced to be proximate to the thermalexpansion coefficient of the optical fiber core line, further, the baseplate made of metal for fixing the silicon platform is formed by 42alloy and therefore, the optical fiber core line is difficult toexfoliate at the support portions, the optical fiber is difficult todisconnect, the transmission and reception efficiency between theoptical fiber and the semiconductor laser element is difficult to varyand the highly reliable photo-electronic device can be provided.

(3) The case is formed by liquid crystal polymer, the base plate isexposed at the bottom of the case, the thickness of resin below the baseplate is thinned and accordingly, heat radiating performance of thephoto-electronic device can be improved and the stably operatedphoto-electronic device can be provided.

(4) Although the case is formed by liquid crystal polymer having lowtensile strength of weld, the thickness of the liquid crystal polymer atthe peripheral edge of the bottom of the case 10 is formed to be thickas the ribs and accordingly, the mechanical strength of the case isincreased and high reliability of the package is promoted.

What is claimed is:
 1. A photo-electronic device comprising: (a) aphotoelectric conversion element having an electrode at a main facethereof; (b) an optical fiber for transmitting and receiving light toand from the photoelectric conversion element; (c) a package comprisinga resin for sealing the photoelectric conversion element and the opticalfiber; (d) a base plate one face of which is exposed from the packageand other face of which is mounted with the photoelectric conversionelement; and (e) a lead electrically connected to an electrode of thephotoelectric conversion element; wherein the base plate is formed by amaterial having a thermal expansion coefficient smaller than a thermalexpansion coefficient of copper.
 2. The photo-electronic deviceaccording to claim 1: wherein the base plate comprises 42 alloy.
 3. Thephoto-electronic device according to claim 1: wherein the base platecomprises kovar.
 4. The photo-electronic device according to claim 2:wherein the photoelectric conversion element is mounted to the baseplate via a support substrate.
 5. The photo-electronic device accordingto claim 4: wherein the support substrate comprises silicon.
 6. Thephoto-electronic device according to claim 2: wherein one end of thelead is electrically connected to the electrode of the photoelectricconversion element at an inner portion of the package and other endthereof is projected to outside of the package.
 7. The photo-electronicdevice according to claim 4: wherein the photo-electronic conversionelement is a semiconductor laser and a photodiode is mounted over thesupport substrate on a side opposed to the optical fiber.
 8. Thephoto-electronic device according to claim 2: wherein the resinconstituting the package comprises a liquid crystal polymer.
 9. Aphoto-electronic device comprising: (a) a photoelectric conversionelement; (b) an optical fiber for transmitting and receiving light toand from the photoelectric conversion element; (c) a case having a mainbody portion having a recess for containing the photoelectric conversionelement and a guide portion for supporting the optical fiber and formedby a resin; (d) a cap having portions in correspondence with the mainbody portion and the guide portion and comprising a resin; (e) a baseplate one face of which is exposed from the case and other face of whichis mounted with the photoelectric conversion element; and (f) a leadelectrically connected to the photoelectric conversion element; whereinthe base plate and the lead comprise 42 alloy.
 10. The photo-electronicdevice according to claim 9: wherein the photoelectric conversionelement is mounted to the base plate via a support substrate and theoptical fiber is fixed onto the support plate.
 11. The photo-electronicdevice according to claim 10: wherein the optical fiber is adhered tothe case at the guide portion.
 12. The photo-electronic device accordingto claim 11: wherein the resin constituting the case comprises a liquidcrystal polymer.
 13. The photo-electronic device according to claim 9:wherein a resin thickness at a portion remote from the base plate isthicker than a resin thickness at a portion in contact with the baseplate.
 14. The photo-electronic device according to claim 13: whereinthe resin constituting the case comprises a liquid crystal polymer. 15.A method of producing a photo-electronic device which is aphoto-electronic device comprising a photoelectric conversion element, abase plate for mounting the photo-electronic device, an optical fiberfor transmitting and receiving light to and from the photoelectricconversion element and a package comprising a resin for sealing thephotoelectric conversion element and the base plate, said methodcomprising the steps of: (a) putting the base plate mounted with thephotoelectric conversion element and the optical fiber positioned to thephotoelectric conversion element into a cavity of resin seal dies; and(b) injecting a resin into the cavity such that the resin is made toflow in a direction of connecting the photoelectric conversion elementand the optical fiber.
 16. The method of producing a photo-electronicdevice according to claim 15: wherein a liquid crystal polymer is usedas the resin.
 17. The method of producing a photo-electronic deviceaccording to claim 15: wherein the resin is injected into the cavity ina state in which a portion of the dies is brought into contact with thebase plate.